78 



THE OAK 



becoming russet-brown in colour. Young oaks retain 

 their dead leaves till far into the winter, and even old 

 trees usually have some leaves attached till January. 

 The young leaves secrete small quantities of sweet 

 liquid on the superior face of the lamina, and are much 

 visited by bees and wasps ; this honey must come 



through the mem- 

 brane. As the leaves 

 approach maturity 

 the lamina becomes 

 bright and hard. 



The arrangement 

 of the leaves is ex- 

 pressed by the frac- 

 tion f, as already de- 

 scribed, each node 

 giving off one leaf at 

 an open angle, the 

 points of insertion 

 being so arranged 

 that a line drawn 

 from the insertion of 

 a given lower leaf, 

 and joining it to the 



points of insertion of those above, passes twice round the 

 twig before we arrive at the leaf situated vertically above 

 the one started from, and this upper leaf is the sixth 

 above. Although this is the commonest and normal 

 arrangement, however, other dispositions are occasionally 



FIG. 21. A portion of the ultimate 

 ramifications of the vascular bundles, 

 showing tracheids only, isolated from 

 the leaf by maceration. 



